| QuinStar Technology’s
QMF series Mode Filters provide a solution to the critical need for mode purity when using
TE01 mode circular waveguide. Due to the similarities between the TE01 and TM11 modes,
even the slightest irregularities in the circular waveguide cause mode conversion from
TE01 to TM11. The large waveguide diameters will readily propagate TEM1 modes, which
degrade the purity of the TE01 signal. Extraneous TEM1 and TEMN modes cannot be
reconverted to the TE10-rectangular mode – they show up as large spurious losses.
Each QMF series
mode filter consists of a section of lossy wall waveguide. Because the higher order modes
(TMM1, TEMN) have wall currents, they are sharply attenuated and do not propagate. |
Although the energy transferred to these modes is minimal, mode filters must
be placed periodically along the transmission line. The TE01 mode, which does not have
wall currents, passes through this section unaffected. The QMF series mode filters are
available in circular waveguide sizes from 12.4 to 140 GHz. They are fitted with one male
and one female type of QuinStar’s standard circular flanges.
The QMF series
mode filters are used to prevent TE01 conversion to higher order modes. By attenuating
unwanted TEM1 modes, the 340 series filters allow for the low loss transmission of TE01,
TE02 modes in circular waveguide and eliminate unwanted resonance, it is recommended that
the QMF series filters be placed at least every 10 feet apart. |
